Is there something I can do to prevent my apple trees from getting woolly aphids? I’d rather not have to spray anything.
Encouraging beneficial insects is one step you can take. A 2013 study at Washington State University found that planting Alyssum flowers attracted syrphids which did a good job of reducing woolly aphid populations. Here are highlights of the paper that was published based on the study’s findings:
- Sweet alyssum flowers had the highest attractiveness to syrphids.
- Faster suppression of woolly apple aphid occurred on trees closer to alyssum flowers.
- Higher densities of natural enemies were observed near sweet alyssum plantings.
- Natural enemies were found to move between sweet alyssum and adjacent apple trees.
As Washington State University’s HortSense website (search under “tree fruit,” “apple,” then “aphids”) indicates, encouraging beneficial insects is a good practice for the control of all 3 main types of aphids affecting apples, be they woolly, rosy, or green:
- Control honeydew-feeding ants, which may protect aphid colonies from predators.
- Encourage natural predators including ladybird beetles, lacewings, syrphid (hover) fly larvae, and parasitic wasps. Avoid use of broad-spectrum insecticides which kill these beneficial insects.
- Hand-wipe or prune to control small, localized infestations (when practical).
- Provide proper nutrition. High levels of nitrogen encourage aphid reproduction. Switch to a slow-release or low-nitrogen fertilizer.
- Wash aphids from tree with a strong stream of water before leaves curl.